For tens of millions of Iranians, Telegram is an indispensable tool. The popular encrypted messaging app is used by half the population for everything from sharing videos with family and friends to conducting business to engaging in political debate. Over the years it has even become a common means of communication among state officials and institutions.

But the April 18 announcement that government bodies are now banned from using foreign messaging apps, including Telegram -- amid calls by lawmakers for Telegram to be banned outright -- raises questions among Iranians who want to share information without fear of retribution.

After all, the authorities have attempted in the past to block Telegram in an effort to deny antiestablishment types a means of secure communication.

In the face of the possibility that Telegram could be blocked entirely, the authorities have been promoting domestic alternatives to fill the void, prompting some Iranians to vow to keep using the app via antifiltering tools.

Supreme Leader Ayatollah Ali Khamenei himself has been trumpeting the security of homegrown messaging services, jumping the gun on the April 18 ban announcement by saying that he personally would no longer be using Telegram, and would be switching to three domestic alternatives.

The revelation came after he tried to sell the Iranian people on the security of homegrown messaging options in an apparent attempt to assuage fears among citizens that personal data and information could be shared with security bodies.

"The officials must safeguard the people's and the country's security and privacy," Khamenei said in an April 9 meeting, according to his official website. "Invading the privacy and security of the people is religiously forbidden, against Islamic law, and must not be undertaken," he was quoted as saying.

The comments, which officials and state media praised as a "historic fatwa," followed forewarnings by officials and lawmakers that Telegram could be blocked.

Supreme Cyberspace Council Secretary Abolhassan Firouzabadi -- who admitted that he personally uses both Telegram and Instagram -- said on April 16 that Telegram could be blocked "any minute," while two conservative lawmakers had said it could be blocked as early as April 21.

Senior officials had attempted on their own to assure potential users of domestic apps that their confidentiality would be compromised. "No message is read, and no information is communicated to anyone," Communications Minister Mohammad Javad Azari Jahromi told lawmakers last week.

But even Khamenei's claim that violating online privacy was prohibited in the Islamic republic appeared to do little to allay the concerns of Iranians who've grown accustomed to state interference in different aspects of their lives, including their personal appearance.

One user reacted to Khamenei's statement by posting a short video of nine surveillance videos following the movements of a paper airplane, saying that's how she views the domestic communications app Soroush that has been promoted as one of the main replacements for Telegram.

"My image of the communications app Soroush when you want to send content : ))," Ghazal wrote with the hashtag #religiouslyforbidden.

Those who are politically active face a greater degree of state scrutiny and violation of their privacy.

Former political prisoners have told RFE/RL that their interrogators often show them copies of their social-media posts, e-mails, and text messages, which are then used against them.

Some have also said that they had been forced to give the passwords to their social-media accounts to their interrogators. They were also interrogated about their sex lives.

User Parastoo, a feminist who shared her experience when arrested in Iran, wrote on Twitter that her interrogators had pressed her to disclose whether she was a virgin or not.

"During the interrogation, I was asked several times whether I was a virgin. I said every time that I won't answer and that if they needed to know for my case, they should refer me to the coroner," she tweeted.

In a sign that the fear over online privacy was justified, Soroush manager Meysam Seyed Salehi said before Khamenei's "fatwa" that his company had received "requests" for users' information. "We received requests that were not answered and we were pressured for not answering," he said in an interview.

He claimed that after Khamenei's April 9 assurances, his company hadn't responded to any "security request" with "peace of mind."

Amid the drive in favor of homegrown messaging apps, the Education Ministry banned the use of foreign social-media apps, including Telegram and Instagram, at schools, the semiofficial ILNA news agency reported.